US considers smaller nuclear reactors

NY Times News Service, Washington

The Tennessee Valley Authority (TVA) will pay Babcock & Wilcox, a nuclear equipment company, to complete extensive design work and apply for permission to build a new kind of nuclear plant, a “small modular reactor,” at a site in Oak Ridge, Tennessee, the authority and the company announced on Wednesday.

The two entities did not disclose the value of the contract, which will be paid in part by the US Department of Energy under a program to encourage nuclear innovation.

The announcement is a step forward in a program that advocates hope will develop a new class of nuclear plants that can be mostly built in a factory, shipped by rail or barge, deployed quickly and sold around the world, especially in places where the power grid could not handle a big plant.

Because the reactors are relatively small, the idea is that in an emergency they can be cooled with the natural circulation of water and heat, rather than by systems that require pumps and valves and that could be disabled by power failures or human errors.

The goal for Babcock & Wilcox is a reactor that can be operated by a relatively small control room crew, perhaps two operators, and meet security requirements with fewer guards.

Babcock & Wilcox mPower president Christofer Mowry said that existing big reactors rely on a “force on force concept,” with armed guards prepared to repel armed intruders, while the mPower concept was “force on concrete,” with a reactor that is housed under a concrete slab.

“That’s a lot easier to defend,” he said.

The reactor is intended as a direct challenge to natural gas generators, and it is intended to share two characteristics that make gas attractive.

First, the builders say they can be built quickly and be added onto later, so there is less risk of building too much capacity or running short.

Second, they are meant to do something that is difficult for existing nuclear plants but easy for gas: change power output rapidly.

Grid operators are increasingly challenged by having to integrate large amounts of power from wind farms and solar installations, which can experience surges or drops in output. Planners are looking for supply partners for those variable generators.

Mowry said his company wanted to have the first of two units in service at Oak Ridge by 2022, an aggressive schedule that he said was “eight years and change.”

The US Department of Energy could match costs up to 50 percent, depending in part on how much the US Congress allocates.

No one has built reactors of that size in the US since the 1960s, but the concept of reviving small reactors has been around in one form or another for 20 years.

Four giant reactors intended to be “passively safe” are under construction but few seem likely to follow soon.

Two years after Japan’s Fukushima Dai-ichi accident, in an era of low natural gas prices, the small reactor concept is the most popular one in the field.

The company has been lining up suppliers and completing design details.

However, small is a relative term — the vessel is 3.96m in diameter and 25.29m high.

The idea is for a 180-megawatt reactor, which is about one-sixth the size of new conventional reactors, but about the size of some old coal units now being retired.

“One of the impediments to new nuclear is the sheer scale of the financial commitment,” said Marc Chupka, an economist and consultant at the Brattle Group who specializes in electricity.